Vacuum snubber



Jan. 5, 1932.

F. TRANSOM VACUUM SNUBBER Filed Feb. 5, 1927 Patented Jan. ,5, 1932UNITED STATES PATENT OFFICE VACUUM SNUBBER Application filed February 5,1927. Serial No. 166,209.

`My invention relates to improvements iny vacuum snubbers as used moreparticularly onan automobile as a rebound check. The general operationof these devices is well known to those skilled in the art; but see, forinstance, patent to P. F. Halferty No. 1,392,- 150, granted Sept. 27,1921, as disclosing a vacuum rebound check, on which this invention maybe considered to be further vimprovements.

One object of my invention is to co-ordinate the snubbing action of thedevice with the up and down movements of the car body after it hasencountered a road obstacle.

Another object of my invention is to provide a device of this characterwhich will be capable of applying almost full atmospheric pressure toarresting abnormal. body movements. v'

Another object of the invention is to cause the full strength of the'snubber to act immediately lon the upward throw of the car body,y and tocease to act immediately when the car body begins to drop towards itsnormal riding position'on its leaf springs.

lAnother object is to substantially eliminate all snubbing actiondependent upon mechanical springs.

Other objects and advantages ofmy invention will appear in connectionwith the following description of the several figures of theaccompanying drawings which constitute apart of this specification, andin which Fig. 1 shows somewhat diagrammatically an automobile frame, orchassis, resting'on leaf springs in normal riding position.

Fig. 2 isa similar view of these parts showing the leaf springscompressed, due to the wheel hitting a road obstacle.

Fig, 3-is a side elevation of my vacuum snubber.

Fig. 4 is a top plan view of the parts shownv in Fig. 3.

Fig. 5 is a rear end elevation of the snubber cylinder. l

Fig. 6 is a front end elevation of the snubber cylinder.

' Fig. v7 is a detail view, showing part of the valve mechanism.

The snubber mechanism of this application comprises a cylinder 5,mounted on the chassis of a vehicle and provided with an air tightpiston 7, slidably mounted in the cylinder, and constantly urged, orimpelled, by a spring 8 towards one end of the cylinder, 55 the otherend of the cylinder serving as an abutment against which spring 8thrusts.

My improvements begin with the design of the spring 8. Hitherto thisspring has been designed to contribute materially to arrest 60 the pullof strap 6 on the piston. The disadvantage of such an action is thatwhen the car body has come to rest on its upward throw, and begins todescend, spring 8 is still pulling on strap 6 a full maximum pull, whichhas now become harmful, and there is no way to overcome such a resultentirely, but it can be very greatly minimized, by restricting thevfunction of the spring 8 simply to returning piston 7 to initialposition, to "0 enable it to promptly set up a new vacuum as needed,when strap 6 pulls to snub the neXt throw upwardly of the car.

As shown in Figs. 3, 4; and 6 the strap 6 passes over a pulley, orroller 11. The movement of this roller is governed in direction; i. e.,clockwise or the reverse, by strap 6. As long as strap 6 is paying outof the cylinder, roller 11 will turn anticlockwise, the instant strap 6reverses and works into cylinder 5 roller 11 will turn clockwise. In myinvention this action is utilized to determine the precise instant atwhich the snubbing action of the device is to cease, so as not to put c,any harmful additional pressure on the chassis during its down stroke,or oscillation.

The way the control of the snubbing effect is brought about as referredto in the last paragraph will be understood by noting that roller 11 iskeyed to a pin 12, which rotates in bearings in the cheeks cast with thefront cylinder end 10. This pin 12 carries an integral head, shaped as aratchet wheel 14. Mounted on a roller bearing, which is itself (.1,carriedV on a boss, cast with cheek 13, is a cam wheel 15. The cam wheel15 is free to rotate on its roller bearing, except for pawl engagementwith ratchet wheel 111. When ratchet wheel 14 turns clockwise it carriescam wheel 15 with it. When ratchet wheel 14 turns anti-clockwise, itsmovement does not affect cam wheel 15, which then rests idle.

The two end heads 9 and 10 are each provided with a lug 23. These lugsslidably support a tappet bar 24, which has a roller 25 at one end,engaging-cam wheell. The other end of the bar Q4 bears against afollower plate 20 on which is fixed a leather washer 21, adapted to makea tight joint with a valve seat 17, cast integral with cylinder end 9.The follower plate 20 is held up against seat 17 by a spring 19 housedin a cover cap 18, screwed to seat 17. The operation of the partsdescribed will be obvious-when bar 24 presses against plate 2O itwilllopen'V the valve 17, thus causing free communication between theVinterior of the cylinder and the atmosphere. lVith valve 17 open onlyatmospheric pressure can exist in cylinder 5. Vith valve 17 closed avacuum can be formed in cylinder 5 of nearly 15 lbs. per square y inch,depending on altitude and temperature of the place a car may be. I haveshown piston 7 madeair tight by a cup leather, but obviously pistonrings may be used for this purpose.

From the above detailed description of the mechanism used in myinvention it will bek seen, referring to Fig. 2, when the auto wheelhits an obstruction, leaf spring 3 will be flattened out, and thechassis will-drop towards the axle. This allows strap 6 to work intocylinder 5, and ifA the shock is severe enough, spring 8 will drivepiston 7 all the way back until it brings up against cylinder head 9, asshown in Figs. 2 and A4. Spring 3 then begins to resume its upwardcurvature, and in doing soY throws the chassis away from it,simultaneously pulling strap 6 out ofv cylinder 5, and movingl piston 7away from cylinder head 9. This results in setting up avacuum betweenthe piston and the cylinder head it had been resting against. Duringthis direction of motion of strap 6, roller 11 will be turning counterclockwise, and ratchet wheel 14 will slip over its pawl withoutengagement, leaving cam wheel 15' stationary, held by roller 25, actingasa detent. The: instant spring 3 ceases its `upward thrust, which willbe beyond its neutral position (normal ridingl position) the strap 6will reverse its direction of movement, and immediately pawl 16, willdrop into a ratchet tooth and cause cam wheel 15 to turn clockwise.-This will propel bar 24 against the follower plate 20 and thus open thevalve 17. The eii'ect of opening this` valve will be to break the vacuumin cylinder 5 at the instant the chassis begins its down stroke, oroscillation, which occurs at the same time strap 6 reverses itsdirection of motion; furthermore bar 24 will tap the valve 17 openthroughout the return stroke of piston 7`, thus preventing the buildingup of a back pressure inv the cylinder ahead of the piston. With thevacuum overcome the chassis is free to settle on its leaf springs,simply with a momentum due only to the weight of the car body, and thedisturbance will come quickly to an end, instead of going into a seriesof oscillations.

It will thus be seen the invention gives an instantaneous snubbingaction at'the precise moment it is necessary to exert it, and thissnubbing action is removed also at the precise moment in which it tendsto become detrimental to the steadiness of riding of the car body. Alsothis operation is self graduating, if the shock is a slight one thepiston 7 will be near its normal position .as shown in Figs. 1 and 3,and there will be considerable airin cylinder 5. If the shock is a heavyone all the air in cylinder 5 will be expelled through valve 17, aspiston 7 approaches cylinder head 9, valve 17 being held practicallycontinuously open by a series of taps given to the follower plate 20, bytappet bar 24, as long as strap 6 is working into the cylinder. i/Vhenpiston 7 lreaches head 9 it is in a position tocause an almost completevacuum on f its out stroke. l y

The leaf spring systemof an automobile can withstand ,a heavy shocktending to compress, or iia'tten out, the leaf springs, the design ofthese springs being such that the closer they are pressed together thestiffer the resistance becomes to further compres-y sion. On the otherhand when the rebound takes place the entire energy of these powerfulsprings is exerted to-hurl the car body away from its axles and afterthe springs have once passed their normal riding position the furthermotion of the car body becomes dangerous because instead of compressingthe leaves of the springs on each other the momentum of the car body,upwardly directed, tends to pull the springs apart and they becomeprogressively weaker instead of progressively stronger as when undercompression. The remedy is to begin to snub instantlyv andproportionally to the upward thrust of the springs and to desist fromsnubbing the instant the upward momentum of the car body has beenovercome, letting it settle easily to normal position again.

The operative principle of the invention has been illustrated as applied-to the design of a standard form of vacuum snubber mechanism,comprising a cylinder provided with a slidable piston, constituting ineffect a chamber with a movable wall, but it will be seen that theessential-principle involvedcan be'carried out in other forms ofconstruction giving a chamber withv variable cubic air contents, andadapted to be filled either with air at atmospheric pressure, oralternately, to develop a more or less pronounced vacuum within itswalls, according as the shock to be resisted is great or small, all asexplained in detail in this specification, in considering the effect ofdifferent lengths of piston stroke.

Also, while the invention has been described in connection with the upand down oscillations of an automobile car body with respect to itsaxles, obviously the snubber principle involved need not be restrictedto the arrest of up and down movements, nor need the mass in oscillationbe that of a car body, for instance a movement of displacement of anyheavy body, developing a strong rebound towards a neutral position, maybe arrested without causing a harmful addition to the rebound action.

Having fully described is claimed as novel is:

l. In a snubber device, a vacuum cylinder, a piston therein, a valvemounted on said cylinder, means associated with a vehicle chassis foractuating said piston to induce a vacuum in the cylinder in onedirection of piston movement and a trip mechanism designed to open saidvalve the instant the piston reverses its motion.

2. In a vehicle snubber, a cylinder, a piston reciprocate'd therein bymeans responsive to .up and down movements of the vehicle body and cammechanism actuated by said means and provided with parts designed to fixa point of vacuum release for said cylinder at one end of each pistonreciprocation.

3. In a vacuum snubber, a cylinder, a spring pressed piston therein, astrap connected to said piston, avalve at one end of the cylinder, andmeans actuated by the said strap while running into the cylinder foropening said valve.

4. In a vacuum snubber device, a vacuum chamber comprising an elementdesigned to be mounted on a car body and a complementary elementdesigned to be attached to a car axle, in combination with vacuum valvemeans on one of said elements, operable by engagement with the otherelement, whereby all movements of separation between the car body andits axle take place under a snubbing action, while all movements ofapproach of those parts take place free from snubbing action.

5. An automobile rebound check comprising an air cylinder, designed tobe mounted on a vehicle chassis, a piston therein, driving means forsaid piston, a valve and valve operating means associated with saidcylinder designed to open the cylinder to atmospheric pressure under thecontrol of the piston driving means and synchronously with up and downmovements of the vehicle chassis.

6. A vacuum snubber device for vehicles comprising a cylinder attachedto the vehicle, a piston therein operating to form a vacuum in saidcylinder through the agency of a oneway drive connection with a part ofthe vehicle relatively movable with respect to the cylinder attachment,and vacuum release my invention, what means including a valve andoperating means therefor designed to establish atmospheric pressurewithin the cylinder the instant the piston reverses its motion, incombination with resilient means acting to constantly thrust the pistonwith zero clearance against one end of the cylinder.

7. In a vacuum snubber device, a. vacuum chamber comprising an elementdesigned to be mounted on an oscillatory body, in combination with acomplementary element designed to be mounted on a support for said body,vacuum valve means on one of said elements and one-way acting valveoperating means on the other of said elements, whereby all movements ofseparation between the oscillatory body and its support are resisted bya snubber action set up by said vacuum chamber,'and all movements ofapproach between those parts take place free from snubbing action.

8. In a vacuum snubber, a cylinder, a piston adapted to form a vacuum insaid cylinder, and vacuum release means acting under the control of amechanical connection with said piston for terminating the vacuum periodin the cylinder on a reversal in direction of piston movement.

FREDERICK TRANSOM.

